It sounds like you might have had trouble with dialogue. Worm controls and general exposition was all in the first scene (bedroom). I've listed in depth controls for how to move to the next text field, cancel dialogue early, etc. It sounds like you might not have been reaching dialogue prompts that would have explained things like controls for the worm or why you were on the adventure in the first place.
You are "fetching" your parents. You also play "fetch" by long pressing b (or left shift or right click). I'll likely add some sort of throwing animation to show you're readying the stick to throw in a future update.
Armor stands are just dropping health packs, nothing special there unless you are low on health. I'll adjust their heart color and dialougue prompt to clear up this misconception.
We were pressed for time by the end, so the spider is just a slime with no gravity. The whole thing is practically a hitbox. I found the worm to be pretty ineffective at reaching the spiders floatyness, but it's certainly possible if you shmoove on him in the right ways. There's no "right" way to beat him so long as you're using the games mechanics lol. Congrats on slaying the spider king